Image signal output device and method, and image data conversion device, method, and program

ABSTRACT

An image signal output device including an acquisition section configured to acquire a fundus image, a selection section configured to select a projection for displaying the acquired fundus image from plural projections, a conversion section configured to convert the fundus image into the selected projection, and a processing section configured to output an image signal of the converted fundus image.

FIELD

The present invention relates to an image signal output device andmethod, and to an image data conversion device, method, and program.

BACKGROUND ART

In the disclosure of Patent Document 1, the fundus of an eye is imagedand displayed on a display section. When two points on a displayedfundus image are specified, an actual distance in the fundus iscalculated from a coordinate distance on a mask display screen on afundus with a size computed according to a subject eye diopter and aneye axial length, and the coordinate distance between the two specifiedpoints on the display screen (see for example Patent Document 1).

PATENT DOCUMENT

Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No.2006-122160

SUMMARY OF INVENTION

An image signal output device of a first aspect of the technologydisclosed herein includes an acquisition section configured to acquire afundus image, a selection section configured to select a projection fordisplaying the acquired fundus image from plural projections, aconversion section configured to convert the fundus image into theselected projection, and a processing section configured to output animage signal of the converted fundus image.

A second aspect includes an acquisition section configured to acquire aconformal fundus image, a selection section configured to select afundus image projection, a conversion section configured to convert afundus image into the selected projection, and a processing sectionconfigured to output a first image signal of the conformal fundus imageacquired by the acquisition section and to output a second image signalof a fundus image converted into the selected projection in cases inwhich a projection selection is made by the selection section.

A third aspect includes an acquisition section configured to acquire afundus image, and a conversion section configured to convert image dataof the acquired fundus image into virtual spherical surface image datawith three-dimensional spherical surface coordinates, and to convert theconverted virtual spherical surface image data into at least one out oftwo-dimensional coordinate image data according to a conformalprojection, two-dimensional coordinate image data according to anequal-area projection, or two-dimensional coordinate image dataaccording to an equidistant projection.

A fourth aspect is a program to cause a computer to function as theacquisition section, the selection section, the conversion section, andthe processing section of the image signal output device of any one ofthe first aspect to the eleventh aspect.

A fifth aspect is a program to cause a computer to function as theacquisition section and the conversion section of the image dataconversion device of either the twelfth aspect or the thirteenth aspect.

An image signal output method of a sixth aspect includes by a computer,acquiring a fundus image, by the computer, selecting a projection todisplay the acquired fundus image from out of plural projections, by thecomputer, converting the fundus image into the selected projection, andby the computer, outputting an image signal of the converted fundusimage.

An image signal output method of a seventh aspect includes by acomputer, acquiring a conformal fundus image, by the computer, selectinga fundus image projection, by the computer, converting a fundus imageinto the selected projection, and by the computer, outputting a firstimage signal of the acquired conformal fundus image and outputting asecond image signal of the fundus image converted into the projection.

An image signal output method of an eighth aspect includes: by acomputer, acquiring a fundus image, by the computer, convertingcoordinate data of the acquired fundus image into three-dimensionalspherical surface coordinate data with three-dimensional sphericalsurface coordinates, and converting the converted three-dimensionalspherical surface coordinate data into at least one out of coordinatedata with two-dimensional coordinates according to a conformalprojection, coordinate data with two-dimensional coordinates accordingto an equal-area projection, or coordinate data with two-dimensionalcoordinates according to an equidistant projection.

An image signal output device of a ninth aspect includes an acquisitionsection configured to acquire a fundus image, and a processing sectionconfigured to output an image signal of a fundus image of the acquiredfundus image converted in an equidistant mode, an equal-area mode, or aconformal mode.

A tenth aspect is a program to cause a computer to function as theacquisition section and the processing section of the image signalprocessing device of the ninth aspect.

An image signal processing method of an eleventh aspect includes by acomputer, acquiring a fundus image, and by the computer, outputting animage signal of a fundus image of the acquired fundus image converted inan equidistant mode, an equal-area mode, or a conformal mode.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a fundus image display system100.

FIG. 2 is a functional block diagram illustrating an example of overallconfiguration of an ophthalmic imaging device 110.

FIG. 3 is a schematic view outlining an example of configuration of ascanning device included in an ophthalmic imaging device 110.

FIG. 4A is a block diagram illustrating configuration of an electricalsystem of an image viewer 150.

FIG. 4B is a functional block diagram illustrating an image viewer 150.

FIG. 5 is a flowchart illustrating a fundus image display programexecuted by a CPU 162 of an image viewer 150.

FIG. 6 is a diagram illustrating a fundus image display screen 300 in aconformal display mode.

FIG. 7 is a diagram illustrating a fundus image display screen 300 whena projection selection region 302 has been clicked to display selectionbuttons to select respective projections.

FIG. 8 is a diagram illustrating a fundus image display screen 300 in anequidistant display mode in which a UWF fundus image is displayed in anequidistant projection.

FIG. 9 is a diagram illustrating a fundus image display screen 300 in anequal-area display mode in which a UWF fundus image is displayed in anequal-area projection.

FIG. 10 is a diagram illustrating a fundus image display screen 300 inan equidistant display mode according to a first modified example.

FIG. 11 is a diagram illustrating a fundus image display screen 300 in aconformal display mode in which a UWF fundus image is displayed in aconformal projection in a second modified example.

FIG. 12 is a flowchart illustrating a fundus image display programexecuted by a CPU 162 of an image viewer 150 according to a sixthmodified example.

FIG. 13 is a flowchart illustrating a fundus image display programexecuted by a CPU 162 of an image viewer 150 according to a seventhmodified example.

FIG. 14 is a flowchart illustrating a fundus image display programexecuted by a CPU 162 of an image viewer 150 according to an eighthmodified example.

DESCRIPTION OF EMBODIMENTS

Detailed explanation follows regarding an exemplary embodiment of thepresent invention, with reference to the drawings.

Explanation follows regarding configuration of a fundus image displaysystem 100, with reference to FIG. 1. As illustrated in FIG. 1, thefundus image display system 100 includes an ophthalmic imaging device110 that captures a fundus image, an image management server 140 thatstores plural fundus images, obtained by imaging the fundi of pluralsubjects with the ophthalmic imaging device 110, associated with subjectIDs, and an image viewer 150 that displays a fundus image acquired bythe image management server 140. The ophthalmic imaging device 110, theimage management server 140, and the image viewer 150 are mutuallyconnected through a network 130. Note that the image viewer 150 is anexample of an image signal output device and an image data conversiondevice of the technology disclosed herein.

Explanation follows regarding an example of configuration of theophthalmic imaging device 110, with reference to FIG. 2. As illustratedin FIG. 2, the ophthalmic imaging device 110 includes a device body 14that images the fundus of a subject eye, and a control device 16. Thecontrol device 16 is configured by a computer including a CPU, RAM, ROM,and an input/output (I/O) port, and is connected to the network 130through a non-illustrated communication interface (I/F). In thefollowing explanation, “imaging” refers to the acquisition by a user ofan image representing an imaging subject using the ophthalmic imagingdevice 110, and is also referred to as “image capture” on occasion. Thedevice body 14 operates under the control of the control device 16. Thedevice body 14 includes an SLO unit 18, a scanning device 19, and an OCTunit 20.

In the following explanation, when the ophthalmic imaging device 110 isinstalled on a horizontal plane, the horizontal direction is referred toas the “Y direction”, a direction perpendicular to the horizontaldirection is referred to as the “X direction”, and a direction from theanterior segment through an eyeball center O toward the fundus of asubject eye 12 is referred to as the “Z direction”. Accordingly, the Xdirection is a direction perpendicular to both the Y direction and the Zdirection.

The ophthalmic imaging device 110 according to the present exemplaryembodiment includes two functions as examples of main functions that canbe implemented by the ophthalmic imaging device 110. The first functionis a function in which the ophthalmic imaging device 110 operates as ascanning laser ophthalmoscope (hereafter SLO) to perform SLO imaging(this function is referred to hereafter as the SLO imaging systemfunction). The second function is a function in which the ophthalmicimaging device 110 operates as an optical coherence tomography(hereafter OCT) device to perform OCT imaging (this function is referredto hereafter as the OCT imaging system function).

Out of the configuration of the ophthalmic imaging device 110, the SLOimaging system function is implemented by the control device 16, the SLOunit 18, and the scanning device 19 that includes a first opticalscanner 22. The SLO unit 18 includes a light source, and a detectionelement, and the like, and is configured to perform image capture of thefundus of the subject eye 12. Namely, the ophthalmic imaging device 110operates in the SLO imaging system function to perform image capture inwhich the fundus (for example an imageable region 12A) of the subjecteye 12 serves as an imaging subject. Specifically, light from the SLOunit 18 (referred to hereafter as SL) light) is passed through the pupilof the subject eye 12 by the scanning device 19, is [0022] scanned inthe X direction (vertical direction) onto the imageable region 12A bythe first optical scanner 22, and is scanned in the Y direction(horizontal direction) by a third optical scanner 29. A fundus imageconfigured by the reflected light is acquired by the SLO unit 18. Notethat since the SLO imaging system function is a known function, detailedexplanation thereof is omitted.

The OCT imaging system function is implemented by the control device 16,the OCT unit 20, and the scanning device 19 that includes a secondoptical scanner 24. The OCT unit 20 includes a light source, aspectrophotometer, a sensor, a reference optical system, and the like,and is configured to capture images of plural tomographic regions in afundus layer thickness direction. Namely, the ophthalmic imaging device110 operates in the OCT imaging system function to capture images oftomographic regions that are regions in the fundus thickness direction(for example the imageable region 12A). Specifically, light from the OCTunit 20 (referred to hereafter as measurement light) is passed throughthe pupil of the subject eye 12 and onto the imageable region 12A by thescanning device 19 while being scanned in the X direction (verticaldirection) by the second optical scanner 24 and being scanned in the Ydirection (horizontal direction) by the third optical scanner 29. Lightreflected from the measurement light interferes with reference light togenerate interference light. The OCT unit 20 detects respective spectralcomponents of the interference light, and the control device 16 employsthe detection results thereof to acquire physical quantities (forexample a tomographic image) representing the tomographic regions. Notethat since the OCT imaging system function is a known function, detailedexplanation thereof is omitted.

In the following explanation, the SLO light and the measurement lightare both light scanned in two dimensions, namely in the X direction andthe Y direction. Accordingly, where it is not necessary to distinguishbetween the SLO light and the measurement light in the explanation, theSLO light and the measurement light are referred to collectively asscanning light.

Note that in the present exemplary embodiment, the ophthalmic imagingdevice 110 including functionality that employs scanning light isdescribed as an example. However, there is no limitation to ophthalmicimaging devices including functionality that employs scanning light, andany functionality enabling observation of the subject eye 12 may beadopted. For example, there is no limitation to shining scanning light,and application may be made to any ophthalmic imaging device includingfunctionality that enables observation of the fundus of the subject eye12 by shining light toward the fundus of the subject eye 12. Namely,there is no limitation to employing light reflected from the subject eye12 by scanning with scanning light, and functionality to observe thesubject eye 12 simply by shining light is also acceptable. There is,moreover, no limitation to shining light into the subject eye 12. Forexample, functionality to observe the subject eye 12 using light such asfluorescent light generated in the subject eye 12 is also acceptable.Accordingly, light employed when observing the subject eye 12 is aconcept encompassing both light reflected from the fundus and lightgenerated at the fundus. This concept is referred to as “light from thesubject eye 12” in the following explanation.

Explanation follows regarding configuration of the scanning deviceincluded in the ophthalmic imaging device 110, with reference to FIG. 3.As illustrated in FIG. 3, a common optical system 28 includes a slitmirror 30 and an elliptical mirror 32 as well as the third opticalscanner 29. Note that a dichroic mirror 26, the slit mirror 30, and theelliptical mirror 32 are illustrated in an end-on side view. Note thatthe common optical system 28 may be configured by a set of plural lensesinstead of by the slit mirror 30 and the elliptical mirror 32.

The slit mirror 30 includes an elliptical first reflecting face 30A. Thefirst reflecting face 30A has first focal points P1 and a second focalpoint P2. The elliptical mirror 32 also includes an elliptical secondreflecting face 32A. The second reflecting face 32A has a first focalpoint P3 and a second focal point P4.

The slit mirror 30, the elliptical mirror 32, and the third opticalscanner 29 are disposed such that the first focal point P3 and thesecond focal point P2 are both located at a common position at the thirdoptical scanner 29. The slit mirror 30, the elliptical mirror 32, andthe third optical scanner 29 are also disposed such that the secondfocal point P4 is positioned at the center of the pupil of the subjecteye 12. Moreover, the first optical scanner 22, the second opticalscanner 24, and the slit mirror 30 are disposed such that the firstfocal points P1 are positioned at the first optical scanner 22 and thesecond optical scanner 24.

Namely, the first optical scanner 22, the second optical scanner 24, andthe third optical scanner 29 are [0030] disposed at conjugate positionsto the center of the pupil of the subject eye 12.

Note that the configurations disclosed in Japanese Patent Nos. 3490088and 5330236 may be employed for the basic configuration of the scanningdevice 19.

In the present exemplary embodiment, the scanning device illustrated inFIG. 3 has a field of view (FOV) angle of the fundus covering a greaterangle than in technology hitherto, thereby enabling observation of awider range of a fundus region than that achieved by technologyhitherto. Explanation follows regarding the wider range of the fundusregion, with a distinction being made between an external illuminationangle of illumination light shone from the exterior by the ophthalmicimaging device 110 and an internal illumination angle serving as anangle illuminated within the subject eye by this illumination light.

The external illumination angle is an illumination angle of light fromthe ophthalmic imaging device 110, namely, from the exterior of thesubject eye 12. Namely, the external illumination angle is configured bythe angle of light shone toward the fundus of the subject eye 12 headingtoward a pupil center point 27 (namely, a center point of the pupil asviewed face-on (see also FIG. 2)) of the subject eye 12. The externalillumination angle is equivalent to the angle of light reflected fromthe fundus so as to head from the pupil center point 27, out of thesubject eye 12, and toward the ophthalmic imaging device 110.

The internal illumination angle refers to an illumination angle of lighteffectively imaged when the scanning light is shone onto the fundus ofthe subject eye 12, with the eyeball center O of the subject eye 12 as areference position. Although an external illumination angle A and aninternal illumination angle B are in a correspondence relationship,since the following explanation relates to the ophthalmic imagingdevice, the external illumination angle is employed as an illuminationangle corresponding to the field of view angle of the fundus.

The ophthalmic imaging device 110 performs image capture in theimageable region 12A (see also FIG. 2), this being a fundus region ofthe subject eye 12, using the external illumination angle. The imageableregion 12A is, for example, the largest region capable of being scannedby the scanning light from the scanning device 19. One example of theimageable region 12A is the external illumination angle A, providing afield of view over a range of approximately 120°. In such cases, theinternal illumination angle corresponds to an angle of approximately160°.

For example, the imageable region 12A can be broadly split into a firstimageable region 12A1 and a second imageable region 12A2. The firstimageable region 12A1 is a range of a field of view in the vicinity ofan axis of vision CL passing through the pupil center point 27 and thecenter O of the subject eye 12. The second imageable region 12A2 is aperipheral region to the first imageable region 12A1 and is a range in aperipheral field of view away from the axis of vision CL. An example ofthe external illumination angle corresponding to the first imageableregion 12A1 is approximately 300 (corresponding to an internalillumination angle of approximately 45°), and an example of the externalillumination angle corresponding to the second imageable region 12A2 isapproximately 120° (corresponding to an internal illumination angle ofapproximately 1600).

A fundus image obtained by performing image capture of the imageableregion 12A of the subject eye 12 using the ophthalmic imaging device 110is a wider region than that of technology hitherto, and is thus referredto hereafter as an ultra-wide field (UWF) fundus image.

Explanation follows regarding configuration of an electrical system ofthe image viewer 150, with reference to FIG. 4A. As illustrated in FIG.4A, the image viewer 150 includes a computer body 152 provided with aCPU 162, RAM 166, ROM 164, and an input/output (I/O) port 168. Asecondary storage device 154, a display section 156, a mouse 155M, akeyboard 155K, and a communication interface (I/F) 158 are connected tothe input/output (I/O) port 168 of the computer body 152. Theinput/output (I/O) port 168 of the computer body 152 is connected to thenetwork 130 through the communication interface (I/F) 158, enabling theophthalmic imaging device 110 and the image management server 140 tocommunicate with each other. The ROM 164 or the secondary storage device154 is stored with a fundus image display program, described below. Notethat the fundus image display program is an example of a program of thetechnology disclosed herein.

Explanation follows regarding functional configuration of the fundusimage display program executed by the CPU 162 of the image viewer 150,with reference to FIG. 4B. As illustrated in FIG. 4B, the fundus imagedisplay program includes an acquisition function, a selection function,a conversion function, and a processing function. The CPU 162 of theimage viewer 150 functions as an acquisition section 172, a selectionsection 174, a conversion section 176, and a processing section 178 bythe CPU 162 of the image viewer 150 executing the fundus image displayprogram including these functions. The processing section 178 outputs animage signal to the display section 156 as described later, and thedisplay section 156 displays a fundus image based on the image signaloutput by the processing section 178.

Note that although the ophthalmic imaging device 110 includes thedisplay section 156 in the present exemplary embodiment, the technologydisclosed herein is not limited thereto. Configuration may be made inwhich the ophthalmic imaging device 110 does not include the displaysection 156, and a separate display device is provided that isphysically independent of the ophthalmic imaging device 110. In suchcases, the display device may include an image processing processor unitthat operates under the control of the CPU 162, and the image processingprocessor unit may display a fundus image based on an image signaloutput by the processing section 178.

Configuration of an electrical system of the image management server 140is similar to the configuration of the electrical system of the imageviewer 150, and so explanation thereof is omitted.

Explanation follows regarding operation of the present exemplaryembodiment.

In the present exemplary embodiment, a UWF fundus image is displayed inone projection selected from out of three projections.

Explanation follows regarding fundus image display processing of thefundus image display program executed by the acquisition section 172,the selection section 174, the conversion section 176, and theprocessing section 178 of the CPU 162 of the image viewer 150, withreference to FIG. 5. When the fundus image display program illustratedin FIG. 5 starts, at step 200 in FIG. 5 the conversion section 176initializes variables F, G. and H, described later, to zero.

At step 201, the processing section 178 displays a fundus image displayscreen 300 illustrated in FIG. 6 on a screen of the display section 156.

As illustrated in FIG. 6, the fundus image display screen 300 includes aregion displaying a subject ID, subject information (name, age, gender,imaging date and time, left eye/right eye distinguishers, diopters, andso on), [0047] a fundus image display region 304 to display a UWF fundusimage, a projection selection region 302 to select one projection fromout of the three projections mentioned above, a subject selection button306 to select a subject, a red/green balance specify button 308 tospecify the red and green balance in the UWF fundus image, an OCT imagedisplay instruction button 310 to display an OCT image, and an endinstruction button 312 to end the fundus image display processing.Buttons relating to autofluorescence (AF) images, fluoresceinangiography (FA), indocyanine green chorioangiography (ICG) and the likemay also be provided.

Various icons (including buttons to zoom in, zoom out, shift screens,add a description, attach to an email, add freehand annotations, andswitch between left and right, and icons to perform electronic medicalrecord functionality such as referring to past records) may be displayedat an edge of the screen.

Note that the fundus image display screen 300 includes three displaymodes (display configurations) employing the three projections, thesebeing: an equal-area display mode in which a UWF fundus image isdisplayed according to an equal-area projection; an equidistant displaymode in which the UWF fundus image is displayed according to anequidistant projection; and a conformal display mode in which the UWFfundus image is displayed according to a conformal projection. Thefundus image display screen 300 performs display on the processingsection 178 based on the image signal output by the display section 178.

In the equal-area display mode, the fundus image display screen 300displays the UWF fundus image according to an equal-area projection(Lambert azimuthal equal-area projection) such that a ratio of a surfacearea on the fundus to a corresponding surface area in the image is thesame everywhere, regardless of the size of the surface area. This is adisplay mode for correctly ascertaining the surface area of the fundusor a selected specific region of the fundus.

In the equidistant display mode, the fundus image display screen 300displays the UWF fundus image according to an equidistant projection(azimuthal equidistant projection) such that a ratio of the distancefrom a point corresponding to the eye axial center of the fundus toanother point in the image against the distance from the eye axialcenter to another point of the fundus is the same everywhere, regardlessof the distance. This is a display mode for correctly ascertaining thedistance between any given two points on the fundus.

In the conformal display mode, the fundus image display screen 300displays the UWF fundus image according to a conformal projection(stereographic projection) such that angles in the image correspond toangles in the fundus. This is a display mode for correctly ascertainingdirections in the fundus (for example the directions of blood vessels,the orientation of the optical nerve, and the like).

At step 202, when a subject ID is input and an instruction to display afundus image corresponding to the subject ID is input, the acquisitionsection 172 acquires a UWF fundus image corresponding to the subject IDfrom the image management server 140 via the communication interface(I/F) 158. As described above, the UWF fundus image is image data basedon a two-dimensional coordinate format.

At step 204, the UWF fundus image is displayed on the display section156. Specifically, the processing section 178 outputs an image signalfor the UWF fundus image to the display section 156. The display section156 displays the UWF fundus image on the fundus image display region 304based on the output image signal. The fundus image displayed at step 204is a UWF fundus image obtained by the ophthalmic imaging device 110. TheUWF fundus image is configured by coordinate data using atwo-dimensional coordinate format. This is since the ophthalmic imagingdevice 110 scans the fundus in a perpendicular direction (the Ydirection) and in a horizontal function perpendicular to theperpendicular direction (the X direction).

The UWF image is an image obtained using the SLO imaging system functionof the ophthalmic imaging device 110. The SLO imaging system functionscans the fundus with a laser beam pivoting about the pupil of theeyeball. Accordingly, the fundus surface of the eyeball is projectedonto a flat plane as a stereo UWF fundus image. Angles in the UWF fundusimage are therefore the same as those on the eyeball surface, but thesurface areas and distances differ from those in the eyeball. Namely,the UWF fundus image obtained using the SLO imaging system function is afundus image in a conformal projection in which angles are displayedcorrectly.

At step 206, the conversion section 176 calculates (converts) the imagedata of the UWF fundus image acquired at step 202 into virtual sphericalsurface image data in a three-dimensional spherical surface coordinateformat. A virtual spherical surface is data expressing athree-dimensional shape of an eyeball model. An eyeball model that is astandard eyeball model customized using unique subject data, such as theage, ethnicity, and eye axial length of the subject, may configure thevirtual spherical surface.

Specifically, first coordinate data X0, Y0 (unit: pixels) of thetwo-dimensional coordinates of the UWF fundus image are converted intoX, Y (unit: rad).

In the two-dimensional coordinates of the UWF fundus image, the verticalpixel counts are called rows, and the widthwise pixel counts are calledcols.

When the ophthalmic imaging device 110 scans the fundus, the maximumamplitude (angle) in the perpendicular direction (X direction) from theeye axis is 0 rows, and the maximum amplitude (angle) in the horizontaldirection (Y direction) from the eye axis is t0 cols.

X, Y are expressed as follows.

X=(((X0−(rows/2))/(rows))*1)/θrows

Y=(((Y0−(cols/2))/(cols))*1)/θcols

θ cols=100/180 (rad) (in the case of an external illumination angleequivalent to 100°).

Then, virtual spherical surface image data x, y, z is obtained asfollows for the three-dimensional spherical surface coordinates.

x=2X/(1+X2+Y2)

y=2Y/(1+X2+Y2)

z=(−1+X2+Y2)/(1+X2+Y2)

Note that U.S. Pat. Nos. 8,422,750 and 9,649,031 may be employed as amethod for converting the UWF fundus image data into the virtualspherical surface image data with three-dimensional spherical surfacecoordinates. The disclosures of U.S. Pat. No. 8,422,750, filed on Apr.16, 2013, and U.S. Pat. No. 9,649,031, filed on May 16, 2017 areincorporated in their entireties by reference herein.

At step 208, the selection section 174 determines whether or not anoperation instruction for another screen has been given. Specifically,the selection section 174 determines whether or not an operationinstruction for another screen has been given by determining whether ornot any of the subject selection button 306, the red/green balancespecify button 308, the OCT image display instruction button 310, or thelike has been clicked.

In cases in which an operation instruction for another screen isdetermined to have been given at step 208, at step 210 the processingsection 178 outputs data for the other screen to the display section156, and this other screen is displayed on the display section 156.

For example, in cases in which the subject selection button 306 has beenclicked, IDs and subject information for each of plural subjects aredisplayed overlaid on the fundus image display screen 300.

In cases in which the red/green balance specify button 308 has beenclicked, a non-illustrated slider to change the red and green balance ofthe UWF fundus image displayed on the fundus image display region 304 isdisplayed overlaid on the fundus image display screen 300, and the redand green balance of the UWF fundus image is changed according to theoperation position of the slider.

In cases in which the OCT image display instruction button 310 has beenclicked, the ophthalmic imaging device 110 executes the OCT imagingfunction to acquire a tomographic image corresponding to a specifiedportion in the UWF fundus image, and a display screen to display theacquired tomographic image is displayed.

After step 210, the fundus image display processing proceeds to step244.

In cases in which an operation instruction for another screen isdetermined not to have been given at step 208, the selection section 174determines whether or not equidistant projection has been selected.

As illustrated in FIG. 6, an item display instruction button 303 toinstruct respective items representing the three projections isdisplayed in the projection selection region 302. When the item displayinstruction button 303 is clicked, a pulldown menu for the threeprojections is displayed as illustrated in FIG. 7.

The pulldown menu includes a conformal projection instruction button303A to instruct conformal projection, an equal-area projectioninstruction button 303B to instruct equal-area projection, and anequidistant projection instruction button 303C to instruct equidistantprojection.

At step 212, the selection section 174 determines whether or not theequidistant projection instruction button 303C has been clicked in orderto determine whether or not the equidistant display mode has beenselected.

In cases in which determination is made that the equidistant displaymode has not been selected at step 212, at step 224 the selectionsection 174 determines whether or not the equal-area projectioninstruction button 303B has been clicked in order to determine whetheror not the equal-area display mode has been selected.

In cases in which determination is not made that the equal-area displaymode has been selected at step 224, since the conformal projectioninstruction button 303A has been clicked to select the conformal displaymode, the fundus image display processing proceeds to step 236.

In cases in which the equidistant projection is determined to have beenselected at step 212, at step 213 the conversion section 176 determineswhether or not the variable F is 0. In cases in which the variable F is0, at step 214 the conversion section 176 converts virtual sphericalsurface image data, this being three-dimensional spherical surfacecoordinate data, into an equidistant image data format according to theequidistant projection in the following manner.

Specifically, first, the virtual spherical surface image data x, y, zare converted into polar coordinates as follows.

ψ=sin−1(z/√(x2+y2+z2))

λ=cos−1(x/√(x2+y2))(y≥0)

=−cos−1(x/4(x2+y2+z2))(y<0)

Herein, c=cos−1(sin ψ₀ sin ψ+cos γ₀ cos ψ cos(λ−λ₀))

If k′=c/sin (c), equidistant image data X, Y according to theequidistant projection is as follows.

X=−k′{cos ψ₀ sin ψ−sin ψ₀ cos ψ cos(λ−λ₀)}

Y=−k′{cos ψ sin ψ(λ−λ₀)}

ψ₀=−π/2, λ₀=π are entered to obtain the equidistant image data X, Y.

At step 215, the conversion section 176 sets the variable F to 1. Thisstops the conversion processing of step 214 from being repeatedlyexecuted when affirmative determination is repeated at step 212. Incases in which F is not determined to be 0 at step 213, the fundus imagedisplay processing skips steps 214 and 215 and proceeds to step 216.

At step 216, as illustrated in FIG. 8, the processing section 178outputs a signal to the display section 156 including an image signal ofthe equidistant image data X, Y converted at step 214 to the displaysection 156 to generate the fundus image display screen 300 in theequidistant display mode in which the converted UWF equidistant fundusimage is displayed in the fundus image display region 304. The displaysection 156 displays the fundus image display screen 300 in theequidistant display mode in which the converted UWF equidistant fundusimage is displayed in the fundus image display region 304.

At step 218, the processing section 178 outputs a signal to the displaysection 156 to specify and display two points. The display section 156specifies and displays the two points based on the input signal.

As illustrated in FIG. 8, when the fundus image display screen 300 is inthe equidistant display mode, a distance calculation icon region 320 isprovided next to the projection selection region 302 to execute a userinterface to specify two points and instruct calculation of the distancebetween the two points. A point specify button 320A to specify pointsand a distance calculation button 320B to instruct calculation of thedistance between two points are displayed in the distance calculationicon region 320. The user drags the point specify button 320A so as todrag to a desired point in the fundus image display region 304. This isrepeated for a total of two times in order to specify two points 322A,322B.

When the user drags and drops the distance calculation button 320Bbetween the two points on the fundus image display region 304, at step220 the processing section 178 calculates the distance between the twopoints specified at step 218 based on the equidistant image data X, Yconverted at step 214.

At step 222, the processing section 178 displays a value for thedistance calculated at step 220 (for example, 12 mm) next to the twopoints 322A, 322B on the fundus image display region 304. The fundusimage display processing then proceeds to step 244.

Steps 218 to 222 may be repeated plural times to specify plural sets oftwo points, calculate the distance between the two points in each set,and display values calculated as the distances next to each set of twopoints.

There is no limitation to two points being specified. In cases in whicha lesion site in the fundus of the subject has been diagnosed and thelesion site has been stored in advance, at step 218 the image viewer ISOmay display two points at the pre-stored site. The user adjusts the twopoints being displayed while viewing the lesion site in the actualfundus image. In cases in which no adjustment is needed, the distancebetween the two points is calculated as-is.

In cases in which the equal-area projection is determined to have beenselected at step 224, at step 225 the conversion section 176 determineswhether or not the variable G is 0. In cases in which the variable G is0, at step 226 the conversion section 176 converts the virtual sphericalsurface image data into an equal-area image data format according to theequal-area projection in the following manner

Specifically, the conversion section 176 converts the virtual sphericalsurface image data x, y, z into equal-area image data according to theequal-area projection by performing the following conversion.

X=(√(2/(1−z)))*x

Y=(√(2/(1−z)))*y

At step 227, the conversion section 176 sets the variable G to 1. Thefundus image display processing then proceeds to step 228.

In cases in which the variable G is not determined to be 0 at step 225,the fundus image display processing skips step 226 and step 227 andproceeds to step 228.

At step 228, the processing section 178 generates a fundus image displayscreen 300 in the equal-area display mode in which a UWF equal-areafundus image converted into the equal-area projection is displayed inthe fundus image display region 304, based on the equal-area image dataX, Y converted at step 226, and also outputs data for the fundus imagedisplay screen 300 including an image signal for the convertedequal-area image data to the display section 156. The display section156 displays the fundus image display screen 300. The UWF fundus imageis thus displayed in the equal-area projection.

At step 230, the processing section 178 outputs a signal for regionspecification and display to the display section 156. The displaysection 156 specifies and displays a region based on the input signal.

As illustrated in FIG. 9, when the fundus image display screen 300 is inthe equal-area display mode, a surface area calculation icon region 330is displayed next to the projection selection region 302 to execute auser interface to specify an area and calculate the surface area of thisarea. An area specify button 330A to specify an area is displayed in thesurface area calculation icon region 330. The user drags and drops thearea specify button 330A at a desired region in the fundus image displayregion 304. The user then adjusts the size of the 330A after dropping.

At step 232, the processing section 178 calculates the surface area of aregion 330B specified at step 230 based on the equal-area image data X,Y converted at step 226, and at step 234, the processing section 178displays the value (for example 200 mm) of the surface area at 330C nextto the region 330B on the screen of the display section 156. The fundusimage display processing then proceeds to step 244.

Steps 230 to 234 may be repeated plural times to specify a set of pluralareas, calculate the surface area of each area, and display valuescalculated as the surface area next to each of the areas.

There is no limitation to an area being specified. In cases in which alesion site in the fundus of the subject has been diagnosed and thelesion site has been stored in advance, at step 218 the image viewer 150may display a region of the pre-stored site. The user adjusts thedisplayed region while viewing the lesion site in the actual fundusimage. In cases in which no adjustment is needed, the surface area ofthe area is calculated as-is.

In cases in which the equidistant projection is determined not to havebeen selected at step 212 and the equal-area projection is determinednot to have been selected at step 224, determination may be made thatthe conformal projection instruction button 303A has been clicked toselect the conformal projection. The fundus image display processingproceeds to step 236.

At step 236, the conversion section 176 determines whether or not thevariable H is 0. In cases in which the variable H is 0, at step 238 theconversion section 176 converts the virtual spherical surface imagedata, this being three-dimensional spherical surface coordinate data,into a conformal image data format according to the conformal projectionin the following manner. Note that the UWF fundus image acquired at step202 may be employed as-is without converting the virtual sphericalsurface image data into the conformal image data format.

The virtual spherical surface image data is converted into the conformalimage data format in the following manner.

Specifically, the conversion section 176 converts the virtual sphericalsurface image data x, y, z into conformal image data according to theconformal projection by performing the following conversion.

X=x/(1−z)

Y=y(1−z)

At step 240, the conversion section 176 sets the variable H to 1. Thefundus image display processing then proceeds to step 242.

In cases in which the variable H is determined not to be 0 at step 236,the fundus image display processing skips steps 238 and 240 and proceedsto step 242.

At step 242, the processing section 178 generates a fundus image displayscreen 300 in the conformal display mode, in which a UWF conformalfundus image converted from the UWF fundus image into the conformalprojection is displayed in the fundus image display region 304, based onthe conformal image data X, Y converted at step 238, and outputs datafor the fundus image display screen 300 including an image signal forthe converted conformal image data to the display section 156. Thedisplay section 156 displays the fundus image display screen 300. TheUWF fundus image is thus displayed in the conformal projection. Thefundus image display processing then proceeds to step 244.

Although not illustrated in the drawings, the conformal image data maybe employed to calculate the direction between two specified points (theorientation of a straight line defined by two specified points), or tocalculate an angle defined by three specified points (for example, whenthree points, these being a point A, a point B, and a point C, have beenspecified, the angle ∠ABC).

At step 244, the selection section 174 determines whether or not the endinstruction button 312 has been clicked in order to determine whether ornot a finish instruction has been given. In cases in which determinationis made that a finish instruction has not been given at step 244,processing returns to step 208 and the processing described above (step208 to step 244) is executed. In cases in which determination is madethat a finish instruction has been given at step 244, the processing isended.

The equidistant image data converted according to equidistant projectionhas been described as being employed in display of the fundus image inthe equidistant mode and also when calculating the distance between twopoints on the fundus. However, there is no limitation thereto, and theequidistant image data converted according to equidistant projection maybe employed when calculating the distance between two points on thefundus, while a fundus image converted so as to give the user theimpression of an equidistant mode screen may be employed for the fundusimage in the equidistant mode instead of an image converted according toequidistant projection (a fundus image converted not into a trueequidistant projection, but by a conversion method close to that of anequidistant projection).

Similarly, the equal-area image data converted according to equal-areaprojection has been described as being employed in display of the fundusimage in the equal-area mode and also when calculating the surface areaof a region of the fundus. However, there is no limitation thereto, andthe equal-area image data convened according to equal-area projectionmay be employed when calculating the surface area of the fundus, while afundus image converted so as to give the user the impression of anequal-area mode screen may be employed for the fundus image in theequal-area mode instead of an image convened according to equal-areaarea projection (a fundus image converted not into a true equal-areaprojection, but by a conversion method close to that of an equal-areaprojection).

Similarly, the conformal image data converted according to conformalprojection has been described as being employed in display of the fundusimage in the conformal mode and also when calculating the directionbetween two points or an angle defined by three points on the fundus.However, there is no limitation thereto, and the conformal image dataconverted according to conformal projection may be employed whencalculating an angle on the fundus, while a fundus image converted so asto give the user the impression of a conformal mode screen may beemployed for the fundus image in the conformal mode instead of an imageconverted according to the conformal area projection (a fundus imageconverted not into a true conformal projection, but by a conversionmethod close to that of a conformal projection).

In the present exemplary embodiment as described above, the UWF fundusimage is displayed as a fundus image converted according to equal-areaprojection such that the ratio of a surface area on the fundus and acorresponding surface area in the image is the same everywhere,regardless of the size of the surface area. This thereby enablesaccurate surface area measurement and presentation.

Moreover, the UWF fundus image is displayed as a fundus image convenedaccording to equidistant projection such that the distance between twopoints on the fundus appears correctly. This thereby enables accuratedistance measurement and presentation.

Moreover, in the present exemplary embodiment, the UWF fundus image isdisplayed as a UWF fundus image converted according to a projectionselected from out of equal-area projection, equidistant projection, orconformal projection. This enables the UWF fundus image to be displayedsuch that whichever out of surface area, direction, or distance the userdesires appears correctly.

Moreover, in the present exemplary embodiment, two-dimensionalcoordinate image data of the UWF fundus image obtained by the ophthalmicimaging device 110 is converted into virtual spherical surface imagedata with three-dimensional spherical surface coordinates, and theconverted virtual spherical surface image data is converted into imagedata according to the equal-area projection, image data according to theequidistant projection, and image data according to the conformalprojection. Accordingly, the image data converted from the virtualspherical surface image data enables the UWF fundus image to bedisplayed as an image according to equal-area projection, equidistantprojection, and conformal projection.

MODIFIED EXAMPLES

Explanation follows regarding modified examples.

First Modified Example

Explanation follows regarding a fundus image display screen 300according to a first modified example, with reference to FIG. 10. In theexemplary embodiment described above, only a UWF fundus image accordingto a projection selected from the three projections is displayed on thefundus image display screen 300. The technology disclosed herein is notlimited thereto, and UWF fundus images may be displayed in projectionsthat have not been selected as well as a projection that has beenselected. Specifically, in the modified example illustrated in FIG. 10,the fundus image display screen 300 includes the fundus image displayregion 304 of the exemplary embodiment described above, and two fundusimage display regions 350, 360 that are smaller in size than the fundusimage display region 304. A UWF fundus image is displayed in the fundusimage display region 304 in the selected projection, and UWF fundusimages are displayed in the fundus image display regions 350, 360 in theprojections that have not been selected.

In the first modified example, the coordinate data for thetwo-dimensional coordinate data of the UWF fundus image obtained by theophthalmic imaging device 110 is convened into three-dimensionalspherical surface coordinate data for the three-dimensional sphericalsurface coordinates, and the converted three-dimensional sphericalsurface coordinate data is converted in advance into coordinate data oftwo-dimensional coordinate data according to the equal-area projection,coordinate data of two-dimensional coordinate data according to theequidistant projection, and coordinate data of two-dimensionalcoordinate data according to the conformal projection. The UWF fundusimages are then displayed in the fundus image display regions 304, 350,360 employing the image data corresponding to the respective displaymodes.

Second Modified Example

Explanation follows regarding a second modified example. In theexemplary embodiment described above and the first modified example, incases in which the fundus image display screen 300 is displayed in theequidistant display mode as illustrated in FIG. 8, the distance betweentwo specified points is calculated based on the image sign datacorresponding to the equidistant display mode. In cases in which thefundus image display screen 300 is displayed in the equal-area displaymode as illustrated in FIG. 9, the surface area of a specified region iscalculated based on the image data corresponding to the equal-areadisplay mode. However, the technology disclosed herein is not limitedthereto, and a distance or surface area of an area may be calculated anddisplayed on the fundus image display screen 300 when in the conformaldisplay mode, the surface area of an area may be calculated anddisplayed in addition to a distance on the fundus image display screen300 when in the equidistant display mode, or a distance may becalculated and displayed in addition to the surface area of an area onthe fundus image display screen 300 of the equidistant display mode.

For example, as illustrated in FIG. 11, when the fundus image displayscreen 300 is in the conformal display mode in the second modifiedexample, a region displaying the point specify button 320A, the distancecalculation button 320B, and the area specify button 330A is providednext to the projection selection region 302. Although not illustrated inthe drawings, the fundus image display screen 300 in the equidistantdisplay mode and the fundus image display screen 300 in the equal-areadisplay mode are similarly provided with a region displaying the pointspecify button 320A, the distance calculation button 320B, and the areaspecify button 330A next to the projection selection region 302.

In the fundus image display screen 300 in each of the conformal displaymode, the equidistant display mode, and the equal-area display mode,when two points are specified as in the exemplary embodiment describedabove, the distance between the two specified points may be calculatedbased on the image data corresponding to the equidistant display mode.When an area is specified, the surface area of the specified area may becalculated based on the image data corresponding to the equal-areadisplay mode to display calculated values as desired. Similarly to inthe first modified example, in the second modified exampletwo-dimensional coordinate image data of the UWF fundus image obtainedby the ophthalmic imaging device 110 in the first modified example[0134] is converted into the virtual spherical surface image data withthe three-dimensional spherical surface coordinates, and the convertedvirtual spherical surface image data is converted into image data of theequal-area projection, the equidistant projection, and the conformalprojection in advance. The distances and surface areas referred to aboveare calculated based on this converted image data.

Third Modified Example

In the above exemplary embodiment and the first and second modifiedexamples, the UWF fundus image is displayed as a fundus image. However,the technology disclosed herein is not limited thereto, and a fundusimage covering a smaller range than a UWF fundus image may be displayed.

Fourth Modified Example

The above exemplary embodiment and the first to third modified examplesare provided with the ophthalmic imaging device 110, the imagemanagement server 140, and the image viewer 150. However, the technologydisclosed herein is not limited thereto, and may be applied to a firstsystem configuration from which the image management server 140 isomitted, a second system configuration from which the image viewer 150is omitted, or a third system configuration from which both the imagemanagement server 140 and the image viewer 150 are omitted.

In the first system configuration, since the image management server 140is omitted, fundus images of each of plural subjects obtained by theophthalmic imaging device 110 are managed by the ophthalmic imagingdevice 110 or the image viewer 150. In cases in which the fundus imagesof each of the plural subjects are managed by the ophthalmic imagingdevice 110, the image viewer 150 acquires the fundus images from theophthalmic imaging device 110 and executes the fundus image displayprogram.

In the second system configuration, since the image viewer 150 isomitted, fundus images of each of plural subjects obtained by theophthalmic imaging device 110 are managed by the ophthalmic imagingdevice 110 or the image management server 140. In cases in which thefundus images of each of the plural subjects are managed by theophthalmic imaging device 110, the image management server 140 acquiresthe fundus images from the ophthalmic imaging device 110 and executesthe fundus image display program.

In the third system configuration, since both the image managementserver 140 and the image viewer 150 are omitted, fundus images of eachof plural subjects obtained by the ophthalmic imaging device 110 arestored in a storage device by the ophthalmic imaging device 110, and theophthalmic imaging device 110 acquires the fundus images from thestorage device and executes the fundus image display program.

Fifth Modified Example

In the above exemplary embodiment and the first and second modifiedexamples, the UWF fundus image is displayed as the fundus image.However, the technology disclosed herein is not limited thereto, and amontage fundus image may be configured by merging together plural fundusimages. Planar images (en-face images) obtained by processing OCT dataacquired using the OCT imaging system function or planar images obtainedby OCT-angiography may also be employed.

Sixth Modified Example

In a sixth modified example, the acquisition section 172, the selectionsection 174, the conversion section 176, and the processing section 178of the CPU 162 execute a fundus image display program illustrated inFIG. 12 instead of the fundus image display program illustrated in FIG.5.

The fundus image display program illustrated in FIG. 12 is started whenthe fundus image display screen 300 illustrated in FIG. 6 is displayedon the display section 156.

At step 402, similarly to at step 202, the acquisition section 172acquires a UWF fundus image corresponding to the subject ID from theimage management server 140 via the communication interface (I/F) 158 asa first fundus image.

At step 404, the selection section 174 determines whether or not adisplay mode has been selected. Specifically, in cases in which the itemdisplay instruction button 303 in FIG. 6 has been clicked to display thepulldown menu for the three projections as illustrated in FIG. 7, andthe user has clicked the conformal projection instruction button 303A,the equal-area projection instruction button 303B, or the equidistantprojection instruction button 303C, the selection section 174 determinesthat the corresponding mode out of the conformal display mode, theequal-area display mode, or the equidistant display mode has beenselected.

At step 406, the conversion section 172 converts the first fundus imageinto a second fundus image according to the selected display mode.Specifically, similarly to at step 206, the conversion section 172converts the first fundus image into virtual spherical surface imagedata based on an eyeball model. In cases in which the equidistantdisplay mode has been selected, the conversion section 172 converts thevirtual spherical surface image data into the equidistant image dataformat according to the equidistant projection similarly to at step 214,to obtain the second fundus image. In cases in which the equal-areadisplay mode has been selected, the conversion section 176 converts thevirtual spherical surface image data into the equal-area image dataformat according to the equal-area projection similarly to at step 226,to obtain the second fundus image. In cases in which the conformaldisplay mode has been selected, the conversion section 176 converts thevirtual spherical surface image data into the conformal image dataformat according to the conformal projection similarly to at step 238,to obtain the second fundus image.

At step 408, the processing section 178 displays the second fundus imageobtained by the conversion performed at step 406 in the fundus imagedisplay region 304, and also outputs a signal to generate the fundusimage display screen 300 in the selected display mode to the displaysection 156. The display section 156 displays the second fundus imageobtained by the conversion performed at step 406 in the fundus imagedisplay region 304 and displays the fundus image display screen 300 inthe selected display mode. In cases in which the equidistant displaymode has been selected, the fundus image display screen 300 is displayedin the equidistant display mode similarly to at step 216. In cases inwhich the equal-area display mode has been selected, the fundus imagedisplay screen 300 is displayed in the equal-area display mode similarlyto at step 228. In cases in which the conformal display mode has beenselected, the fundus image display screen 300 is displayed in theconformal display mode similarly to at step 242.

In the sixth modified example, an image corresponding to either theequal-area display mode, the equidistant display mode, or the conformaldisplay mode may be acquired as the first fundus image at step 402 (FIG.12). Specifically, first, the acquisition section 172 acquires the UWFfundus image corresponding to the subject ID from the image managementserver 140 through the communication interface (I/F) 158, similarly toat step 202. Similarly to at step 206, the conversion section 176 thencalculates (converts) the image data of the UWF fundus image acquired atstep 202 into virtual spherical surface image data using athree-dimensional spherical surface coordinate format. In cases in whichthe equidistant display mode has been specified in advance, similarly toat step 214, the conversion section 176 acquires the first fundus imageby converting the virtual spherical surface image data into theequidistant image data format according to the equidistant projection.In cases in which the equal-area display mode has been specified inadvance, similarly to at step 226, the conversion section 176 acquiresthe first fundus image by converting the virtual spherical surface imagedata into the equal-area image data format according to the equal-areaprojection. In cases in which the conformal display mode has beenspecified in advance, similarly to at step 238, the conversion section176 acquires the first fundus image by converting the virtual sphericalsurface image data into the conformal image data format according to theconformal projection.

Seventh Modified Example

In a seventh modified example, the acquisition section 172, theselection section 174, the conversion section 176, and the processingsection 178 of the CPU 162 execute the fundus image display programillustrated in FIG. 13 instead of the fundus image display programillustrated in FIG. 5.

The fundus image display program illustrated in FIG. 13 is started whenthe fundus image display screen 300 in FIG. 6 has been displayed on thedisplay section 156.

At step 412, similarly to at step 202 (step 402), the acquisitionsection 172 acquires a UWF fundus image corresponding to the subject IDfrom the image management server 140 via the communication interface(I/F) 158 as a first fundus image.

At step 414, the selection section 174 determines whether or not ananalysis mode has been selected.

An analysis mode is a mode in which image analysis is performed on thefundus image and the results thereof are displayed. For example,analysis modes include an analysis mode for the direction of the opticnerve, an analysis mode to find the size of a lesion (the surface areaof a lesion), and an analysis mode to find the distance betweenstructures on the fundus (for example the distance between the maculaand the optic nerve head).

In the seventh exemplary embodiment, an analysis mode instruction buttonis displayed instead of the item display instruction button 303 in FIG.6 (the pulldown menu including the conformal projection instructionbutton 303A, the equal-area projection instruction button 303B, and theequidistant projection instruction button 303C in FIG. 7). When theanalysis mode instruction button is clicked, an instruction button forthe analysis mode for the direction of the optic nerve, an instructionbutton for the analysis mode to find the size of a lesion, and aninstruction button for the analysis mode to find the distance betweenstructures on the fundus are displayed in a pulldown menu. When the userturns on any of the instruction buttons, the selection section 174determines that the corresponding analysis mode has been selected.

At step 416, the conversion section 172 converts the first fundus imageinto a second fundus image according to the selected analysis mode.

Image data in an appropriate display mode for the corresponding analysismode is specified for each of the analysis modes.

In the analysis mode to find the distance between structures on thefundus, equidistant image data is appropriate since distances are to becalculated. In cases in which the analysis mode to find the distancebetween structures on the fundus has been selected, the conversionsection 172 converts the virtual spherical surface image data into theequidistant image data format according to the equidistant projectionsimilarly to at step 214, to obtain the second fundus image.

In the analysis mode for the size of a lesion, equal-area image data isappropriate since surface area is to be calculated. In cases in whichthe analysis mode for the size of a lesion has been selected, theconversion section 176 converts the virtual spherical surface image datainto the equal-area image data format according to the equal-areaprojection similarly to at step 226, to obtain the second fundus image.

In the analysis mode for direction, conformal image data is appropriatesince direction is to be calculated. In cases in which the analysis modefor direction has been selected, the conversion section 176 converts thevirtual spherical surface image data into the conformal image dataformat according to the conformal projection similarly to at step 238,to obtain the second fundus image.

At step 418, the processing section 178 displays the second fundus imageobtained by the conversion performed at step 416 in the fundus imagedisplay region 304, and also outputs a signal to generate the fundusimage display screen 300 in the selected analysis mode to the displaysection 156. The display section 156 displays the second fundus imageobtained by the conversion performed at step 406 in the fundus imagedisplay region 304 and displays the fundus image display screen 300 inthe selected analysis mode.

In cases in which the analysis mode to find the distance betweenstructures on the fundus has been selected, the fundus image displayscreen 300 is displayed in the equidistant display mode similarly to atstep 216.

In cases in which the analysis mode for the size of a lesion has beenselected, the fundus image display screen 30) is displayed in theequal-area display mode similarly to at step 228.

In cases in which the analysis mode for direction has been selected, thefundus image display screen 300 is displayed in the conformal displaymode similarly to at step 242.

Note that in the seventh modified example, at step 412, an image in anymode out of the equal-area display mode, the equidistant display mode,or the conformal display mode may be acquired as the first fundus image.Specifically, first the acquisition section 172 acquires the UWF fundusimage corresponding to the subject ID from the image management server140 through the communication interface (I/F) 158, similarly to at step202. Similarly to at step 206, the conversion section 176 thencalculates (converts) the image data of the UWF fundus image acquired atstep 202 into virtual spherical surface image data using athree-dimensional spherical surface coordinate format based on aneyeball model. In cases in which the equidistant display mode has beenspecified in advance, similarly to at step 214, the conversion section176 acquires the first fundus image by converting the virtual sphericalsurface image data into the equidistant image data format according tothe equidistant projection. In cases in which the equal-area displaymode has been specified in advance, similarly to at step 226, theconversion section 176 acquires the first fundus image by converting thevirtual spherical surface image data into the equal-area image dataformat according to the equal-area projection. In cases in which theconformal display mode has been specified in advance, similarly to atstep 238, the conversion section 176 acquires the first fundus image byconverting the virtual spherical surface image data into the conformalimage data format according to the conformal projection.

The processing section of the CPU 162 of the image viewer 150 calculatesthe distance between two specified points based on the equidistant imagedata converted based on equidistant projection when in the equidistantmode.

The processing section of the CPU 162 of the image viewer 150 calculatesthe surface area of a specified region based on the equal-area imagedata converted based on equal-area projection when in the equal-areamode.

The processing section of the CPU 162 of the image viewer 150 calculatesthe direction of a line segment defined by two specified points or anangle defined by three points based on the conformal image dataconverted based on conformal projection when in the conformal mode.

Eighth Modified Example

In an eighth modified example, the acquisition section 172, theselection section 174, the conversion section 176, and the processingsection 178 of the CPU 162 execute the fundus image display programillustrated in FIG. 14 instead of the fundus image display programillustrated in FIG. 5.

At step 422, similarly to at step 202 (step 402, step 412), theacquisition section 172 acquires a UWF fundus image corresponding to thesubject ID from the image management server 140 via the communicationinterface (/F) 158 as a first fundus image.

At step 424, the conversion section 176 converts the first fundus imageinto virtual spherical surface image data, and generates respectivefundus images for the equal-area display mode, the equidistant displaymode, and the conformal display mode from the virtual spherical surfaceimage data.

Specifically, first, similarly to at step 206, the conversion section176 converts the image data of the UWF fundus image acquired at step 422into virtual spherical surface image data based on an eyeball model.

Next, similarly to at step 214, the conversion section 176 generates anequidistant image by converting the virtual spherical surface image datainto the equidistant image data format according to the equidistantprojection.

Similarly to at step 226, the conversion section 176 generates anequal-area image by converting the virtual spherical surface image datainto the equal-area image data format according to the equal-areaprojection.

Similarly to at step 238, the conversion section 176 generates aconformal image by the conversion section 176 converting the virtualspherical surface image data into the conformal image data formataccording to the conformal projection.

At step 426, the processing section 178 stores the first fundus image,the equidistant image, the equal-area image, and the conformal imageassociated with each other in the memory (the RAM 166).

At step 428, the selection section 174 determines whether or not theuser has selected a display mode or an analysis mode. In the eighthmodified example, in cases in which a display mode has been selected atstep 428, determination is similar to that at step 404 (see FIG. 12).Moreover, in the eighth modified example, in cases in which an analysismode has been selected at step 428, determination is similar to that atstep 414 (see FIG. 13).

At step 430, the processing section 178 outputs a signal to generate thefundus image display screen 300 in the display mode or analysis modeselected at step 428 to the display section 156. The display section 156displays the fundus image display screen 300) in the selected displaymode or analysis mode.

Ninth Modified Example

In a ninth modified example, the acquisition section 172, the conversionsection 176, and the processing section 178 of the CPU 162 may beconfigured so as to execute the following processing instead of thefundus image display program illustrated in FIG. 5.

Similarly to at step 202, the acquisition section 172 acquires a UWFfundus image corresponding to the subject ID from the image managementserver 140 via the communication interface (I/F) 158 as a first fundusimage.

Similarly to at step 204, the processing section 178 outputs an imagesignal of the UWF fundus image to the display section 156. The displaysection 156 displays the UWF fundus image as-is on the fundus imagedisplay region 304 based on the output image signal.

When the user has specified two points and input an instruction tocalculate the distance between the two specified points on the displayedUWF fundus image, the conversion section 176 converts the image data ofthe UWF fundus image into virtual spherical surface image data, andconverts the virtual spherical surface image data into the equidistantimage data format according to the equidistant projection. Theprocessing section calculates the distance between the two specifiedpoints based on the equidistant image data converted based onequidistant projection in the equidistant mode, and outputs a value forthe distance between the two points to the display section 156. Thedisplay section 156 displays the two points along with the distancebetween the two points.

When the user has specified a region and input an instruction tocalculate the surface area of the specified region on the displayed UWFfundus image, the conversion section 176 converts the image data of theUWF fundus image into virtual spherical surface image data based on aneyeball model, and converts converts the virtual spherical surface imagedata into the equal-area image data format according to the equal-areaprojection. The processing section calculates the surface area of thespecified region based on the equal-area image data converted based onequal-area projection in the equal-area mode, and outputs a value forthe surface area of the specified region to the display section 156. Thedisplay section 156 displays the specified region along with the valuefor the surface area of the specified region.

When the user has specified two points or three points and input aninstruction regarding the direction of a line segment defined by the twospecified points or an angle defined by the specified three points inthe displayed UWF fundus image, the conversion section 176 converts theimage data of the UWF fundus image into virtual spherical surface imagedata, and converts converts the virtual spherical surface image datainto the conformal image data format according to the conformalprojection. The processing section calculates the direction of the linesegment defined by the two specified points or the angle defined by thespecified three points based on the converted conformal image data basedon the conformal projection, and outputs a value expressing thedirection of the line segment defined by the two points or the angledefined by the three points to the display section 156. The displaysection 156 displays the two or three specified points along with thevalue expressing the direction of the line segment defined by the twopoints or the angle defined by the three points.

Other Modified Examples

In the above exemplary embodiment and the first to ninth modifiedexamples, the equal-area display mode, the equidistant display mode, andthe conformal display mode are employed as the three display modes.However, the technology disclosed herein is not limited thereto, andother display modes such as the following may be employed. Examplesinclude display modes according to Mollweide projection, Mercatorprojection, Sanson projection, Mollweide projection, and the like.Moreover, the number of the plural display modes that can be selectedmay be a plural number of display modes other than three display modes.

In the examples of the first exemplary embodiment and the respectivemodified examples, control processing is implemented using a computer bysoftware configurations. However, the technology disclosed herein is notlimited thereto. For example, instead of software configurations using acomputer, the control processing may be executed solely by hardwareconfigurations such as field programmable gate arrays (FPGAs) orapplication specific integrated circuits (ASICs). The control processingmay also be executed by a configuration combining hardwareconfigurations and software configurations.

All cited documents, patent applications, and technical standardsmentioned in the present specification are incorporated by reference inthe present specification to the same extent as if each individual citeddocument, patent application, or technical standard was specifically andindividually indicated to be incorporated by reference.

EXPLANATION OF THE REFERENCE NUMERALS

-   100 fundus image display system-   110 ophthalmic imaging device-   130 network-   140 image management server-   150 image viewer-   152 computer body-   156 display section-   172 acquisition section-   174 selection section-   176 conversion section-   178 processing section-   300 fundus image display screen-   302 projection selection region-   303 item display instruction button-   303A conformal projection instruction button-   303B equal-area projection instruction button-   303C equidistant projection instruction button-   304 fundus image display region-   320 distance calculation icon region-   320A point specify button-   320B distance calculation button-   330 surface area calculation icon region-   330A area specify button-   350, 360 fundus image display region

1. An image signal output device comprising: an acquisition sectionconfigured to acquire a fundus image; a selection section configured toselect a projection for displaying the acquired fundus image from aplurality of projections; a conversion section configured to convert thefundus image into the selected projection; and a processing sectionconfigured to output an image signal of the converted fundus image. 2.The image signal output device of claim 1, wherein the plurality ofprojections include at least a conformal projection, an equidistantprojection, and an equal-area projection.
 3. The image signal outputdevice of claim 2, wherein in cases in which none of the projectionshave been selected by the selection section, the processing sectionoutputs an image signal to display the fundus image according to theconformal projection.
 4. The image signal output device of claim 2,wherein in cases in which the converted fundus image is being displayedin the equidistant projection, the processing section calculates adistance between two specific points and outputs data relating to thecalculated distance.
 5. The image signal output device of claim 2,wherein in cases in which the converted fundus image is being displayedin the equal-area projection, the processing section calculates asurface area of a specific region and outputs data relating to thecalculated surface area.
 6. The image signal output device of claim 1,wherein in cases in which the projection into which the fundus imagethat has already been converted by the conversion section is selected bythe selection section again, the processing section outputs an imagesignal of the fundus image corresponding to the other selectedprojection and already converted by the conversion section.
 7. An imagesignal output device comprising: an acquisition section configured toacquire a conformal fundus image; a selection section configured toselect a fundus image projection; a conversion section configured toconvert a fundus image into the selected projection; and a processingsection configured to output a first image signal of the conformalfundus image acquired by the acquisition section and to output a secondimage signal of a fundus image converted into the selected projection incases in which a projection selection is made by the selection section.8. The image signal output device of claim 7, wherein the conformalfundus image is a fundus image captured by a scanning laserophthalmoscope (SLO).
 9. The image signal output device of claim 7,wherein the conformal fundus image is stored on an image server, and theacquisition section acquires the conformal fundus image from the imageserver.
 10. The image signal output device of claim 1, furthercomprising a display section configured to display at least a fundusimage, wherein: the display section is configured to display the fundusimage based on the output image signal.
 11. The image signal outputdevice of claim 7, further comprising a display section configured todisplay at least a fundus image, wherein: the display section isconfigured to display by default the conformal fundus image based on thefirst image signal, and is configured to display the fundus imageconverted into the selected projection based on the second image signal.12. An image data conversion device comprising: an acquisition sectionconfigured to acquire a fundus image; and a conversion sectionconfigured to convert image data of the acquired fundus image intovirtual spherical surface image data with three-dimensional sphericalsurface coordinates, and to convert the converted virtual sphericalsurface image data into at least one out of two-dimensional coordinateimage data according to a conformal projection, two-dimensionalcoordinate image data according to an equal-area projection, ortwo-dimensional coordinate image data according to an equidistantprojection.
 13. The image data conversion device of claim 12, furthercomprising: a selection section configured to select a projection fordisplaying the acquired fundus image from out of a plurality ofprojections; and a processing section configured to output the convertedimage data corresponding to the selected projection.
 14. A program tocause a computer to function as the acquisition section, the selectionsection, the conversion section, and the processing section of the imagesignal output device of claim
 1. 15. A program to cause a computer tofunction as the acquisition section and the conversion section of theimage data conversion device of claim
 12. 16. An image signal outputmethod comprising: by a computer, acquiring a fundus image; by thecomputer, selecting a projection to display the acquired fundus imagefrom out of a plurality of projections; by the computer, converting thefundus image into the selected projection; and by the computer,outputting an image signal of the converted fundus image.
 17. An imagesignal output method comprising: by a computer, acquiring a conformalfundus image; by the computer, selecting a fundus image projection; bythe computer, converting a fundus image into the selected projection;and by the computer, outputting a first image signal of the acquiredconformal fundus image and outputting a second image signal of thefundus image converted into the projection.
 18. An image data conversionmethod comprising: by a computer, acquiring a fundus image; by thecomputer, converting coordinate data of the acquired fundus image intothree-dimensional spherical surface coordinate data withthree-dimensional spherical surface coordinates, and converting theconverted three-dimensional spherical surface coordinate data into atleast one out of coordinate data with two-dimensional coordinatesaccording to a conformal projection, coordinate data withtwo-dimensional coordinates according to an equal-area projection, orcoordinate data with two-dimensional coordinates according to anequidistant projection.
 19. An image signal output device comprising: anacquisition section configured to acquire a fundus image; and aprocessing section configured to output an image signal of a fundusimage of the acquired fundus image converted in an equidistant mode, anequal-area mode, or a conformal mode.
 20. The image signal output deviceof claim 19, wherein in the equidistant mode, the processing sectioncalculates a distance between two specified points based on equidistantimage data converted based on an equidistant projection.
 21. The imagesignal output device of claim 19, wherein in the equal-area mode, theprocessing section calculates a surface area of a specified region basedon equal-area image data converted based on an equal-area projection.22. The image signal output device of claim 19, wherein in the conformalmode, the processing section calculates a direction of a line segmentdefined by two specified points or calculates an angle defined by threepoints based on conformal image data converted based on a conformalprojection.
 23. The image signal output device of claim 19, wherein theimage signal is an image signal to display a fundus image display screenincluding a converted fundus image.
 24. A program to cause a computer tofunction as the acquisition section and the processing section of theimage signal output device of claim
 19. 25. An image signal outputmethod comprising: by a computer, acquiring a fundus image; and by thecomputer, outputting an image signal of a fundus image of the acquiredfundus image converted in an equidistant mode, an equal-area mode, or aconformal mode.
 26. An image signal output device comprising: anacquisition section configured to acquire a first fundus image capturedby a scanning laser ophthalmoscope (SLO); a processing sectionconfigured to output a first image signal corresponding to a firstdisplay screen that displays the first fundus image and a selection menuof a projection; and a conversion section configured to convert thefirst fundus image to a projection selected at the selection menu andoutput a second fundus image, wherein, in a case in which a projectionis selected at the selection menu, the processing section is configuredto output a second image signal corresponding to a second display screenthat displays the second fundus image and the selection menu.
 27. Animage signal output device comprising: an acquisition section configuredto acquire a first fundus image; a conversion section configured toconvert the first fundus image and generate at least a fundus image byan equidistant projection and a fundus image by an equal-areaprojection; and a processing section configured to output an imagesignal corresponding to a display screen including the first fundusimage, the fundus image by an equidistant projection, the fundus imageby an equal-area projection, and a selection menu to select aprojection.